SEOUL, May 25 (Yonhap) -- U.S. National Security Advisor John Bolton said Saturday North Korea's latest missile launches are violations of U.N. Security Council resolutions banning the communist state from such weapons tests.

He made the remark at a press conference in Tokyo, Reuters reported, ahead of a scheduled state visit to Japan by U.S. President Donald Trump.

Bolton was quoted as saying that there was "no doubt" the missile tests violated UNSC resolutions.

North Korea carried out two firings into the East Sea over a less than one-week period early this month, including two short-range missiles, in an apparent show of frustration over the stalled denuclearization talks with the U.S.

There have been inconsistent assessments from Seoul and Washington over how to classify the missile firings. While the South Korean military has yet to officially define the missile types, Pentagon earlier called them ballistic missiles banned under the UNSC resolutions.

Still, Bolton said the U.S. remains willing to hold talks with North Korea and that it's up to its leader, Kim Jong-un, to "walk through" that door.

He also said Kim should agree to a meeting with Japanese Prime Minister Shinzo Abe, as a way to resume and faciliate the denuclearization talks, deadlocked since the Hanoi summit between Kim and U.S. President Donald Trump produced no deal.

Tensions have risen after the U.S. government said it has seized a North Korean cargo ship on suspicion of shipping coal and other goods in violation of U.N. and U.S. sanctions on the regime.

North Korea's foreign ministry on Friday blamed Washington for the failure of the Hanoi summit and urged the U.S. to change its negotiation approach with "a new method of calculation" if it wants to keep the dialogue alive.

Trump is set to visit South Korea late next month as part of his trip to Asia to discuss the denuclearization of North Korea and alliance issues with South Korean President Moon Jae-in.